Near field communication flex circuit

ABSTRACT

A payment terminal can have a near field communication (NFC) circuit to permit the payment terminal to accept an NFC payment transaction from a payment device of a customer. The NFC circuit can have a first set of components that are located on a printed circuit board in the base of the payment terminal and a second set of components that are mounted on a flex circuit in another region of the payment terminal. The flex circuit can be coupled to the printed circuit board and have an extended portion with a plurality of traces to communicate transmit and receive data between the first set of components and the second set of components. The plurality of traces on the extended portion can have a predetermined length that is greater than or equal to 2.5% of the propagation-medium-specific wavelength of the carrier signal communicated over the traces.

BACKGROUND

Near field communication (“NFC”) devices are capable of communicatingwhen they are placed in close proximity to each other, and may be usedfor transactions such as payment transactions. Each of the NFCcommunication devices includes an antenna and related circuitry such asa matching circuit. A first NFC communication device generates awireless carrier signal at a suitable frequency such as 13.56 MHz andtransmits that signal over its antenna. When the antenna of a second NFCcommunication device is placed in close proximity to the antenna of thefirst NFC communication device, the two devices become inductivelycoupled, such that energy is coupled between the two devices through ashared magnetic field.

When the two NFC communication devices are inductively coupled, eitherof the NFC communication devices may communicate via modulated versionsof the wireless carrier signal. The first NFC communication device maymodify aspects of the wireless carrier signal such as amplitude,frequency, and phase prior to transmission in order to encode data thatis transmitted to the second NFC communication device. During times thatthe first device is not transmitting, the second NFC communicationdevice may encode data that is transmitted to the first NFCcommunication device. The second NFC communication device modifies theinductively coupled signal using techniques such as active or passiveload modulation. The first NFC communication device receives the encodeddata based on the changes to the inductively coupled signal.

The use of NFC for payment transactions requires the antenna of thecustomer's NFC-capable payment device to be placed in close proximity tothe antenna of the merchant's NFC-capable payment terminal in order toinductively couple the NFC communication devices for the exchange databetween the two NFC communication devices. For the convenience of thecustomer, the merchant may want to place the antenna of the NFCcommunication device in a display area of the payment terminal foreasier accessibility by the customer's payment device. However, thedisplay area may not have adequate space for all of the components ofthe NFC communication device thereby requiring the NFC communicationdevice to be placed in a location of the payment terminal that is moredifficult for the customer to access.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure, its nature andvarious advantages will be more apparent upon consideration of thefollowing detailed description, taken in conjunction with theaccompanying drawings in which:

FIG. 1 depicts an illustrative block diagram a power supply, USB hub,merchant terminal and customer terminal of a point-of-sale system inaccordance with some embodiments of the present disclosure;

FIG. 2 depicts an illustrative block diagram of components of themerchant terminal in accordance with some embodiments of the presentdisclosure;

FIG. 3 depicts an illustrative block diagram of components of thecustomer terminal in accordance with some embodiments of the presentdisclosure;

FIG. 4 depicts example steps for performing a payment transaction with amerchant terminal and a customer terminal in accordance with someembodiments of the present disclosure;

FIG. 5 depicts an illustrative block diagram of a near fieldcommunication (NFC) circuit in accordance with some embodiments of thepresent disclosure;

FIG. 6 depicts an illustrative schematic diagram of the flex circuit ofthe NFC circuit of FIG. 5 in accordance with some embodiments of thepresent disclosure;

FIG. 7 depicts an illustrative schematic diagram of the NFC transceiverof the NFC circuit of FIG. 5 in accordance with some embodiments of thepresent disclosure;

FIG. 8 depicts an illustrative schematic diagram of the power amplifiercircuit of the NFC circuit of FIG. 5 in accordance with some embodimentsof the present disclosure;

FIG. 9 depicts an illustrative schematic diagram of the tuning circuitsand antenna of the NFC circuit of FIG. 5 in accordance with someembodiments of the present disclosure;

FIG. 10 depicts an illustrative schematic diagram illustrating therectifier/filtering circuits and first amplifier circuit of the NFCcircuit of FIG. 5 in accordance with some embodiments of the presentdisclosure; and

FIG. 11 depicts an illustrative schematic diagram of the secondamplifier circuit and comparator circuit of the NFC circuit of FIG. 5 inaccordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

A payment terminal can have a near field communication (NFC) circuit topermit the payment terminal to accept an NFC payment transaction from apayment device of a customer. The NFC circuit can have a first set ofcomponents that are mounted on a printed circuit board in the base ofthe payment terminal and a second set of components that are mounted ona flex circuit in another region of the payment terminal. An extendedportion of the flex circuit can be coupled to the printed circuit board.The extended portion of the flex circuit can have a plurality of tracesto communicate, transmit and receive data between the first set ofcomponents and the second set of components of the NFC circuit. Theextended portion of the flex circuit can have a predetermined lengththat is greater than or equal to 2.5% of the propagation-medium-specificwavelength of the frequency of the carrier signal communicated over thetraces on the extended portion of the flex circuit.

The first set of components on the printed circuit board can include anNFC transceiver to generate an outgoing modulated digital signal to betransmitted to the customer based on a payment message. The generatedpayment message from the NFC transceiver can be a differential,amplitude modulated digital signal that is passed through a pair ofinverters to boost the signal for communication over the extendedportion of the flex circuit. The first set of components may alsoinclude, within the receive signal path, amplifier and comparatorcircuits to process the data from an analog data signal based onmodulation of the NFC antenna load by a customer payment device. Theprocessed analog signal may be provided to the NFC transceiver.

The second set of components on the flex circuit can include a poweramplifier to receive the modulated digital signal from the NFCtransceiver and amplify and convert the modulated digital signal to adifferential analog signal, and a tuning circuit to prepare thedifferential analog signal for transmission by an NFC antenna. The poweramplifier can include a termination circuit to receive the modulateddigital signal from the NFC transceiver. The termination circuit can beused for impedance matching of the traces of the extended portion of theflex circuit to minimize or remove transmission line effects that couldoccur on the traces. The receive path of the second set of componentsmay include rectifier/filtering circuits to remove the carrier signalfrom a signal received from the customer via the NFC antenna and anamplifier circuit to communicate the data from the received signal tothe amplifier circuit of the first set of components.

FIG. 1 depicts an illustrative block diagram of a payment system 100 inaccordance with some embodiments of the present disclosure. In oneembodiment, payment system 100 includes a power supply 102, USB hub 104,USB connector 106, USB connector 108, merchant terminal 110, andcustomer terminal 112. These components of point-of-sale system 100facilitate electronic payment transactions between a merchant and acustomer.

In an embodiment, the power supply 102 may connect to an AC power sourceand convert the AC voltage into a DC voltage for use by the componentsof the payment system 100. A DC voltage (e.g., 12 volts) may be providedto the USB hub 104. USB hub 104 may convert the received DC voltage intoa plurality of DC voltages for use in powering circuitry of the USB hub104. The USB hub 104 allows for the merchant terminal 110 to communicatewith a plurality of other USB peripherals, such as a receipt printer,cash drawer, barcode scanner, scale, keyboard, USB-Ethernet dongle/USBMiFi, and other similar peripheral devices. As described herein, the USBhub 104 may also include power supply circuitry that selectively allowsthe USB hub to provide a power supply signal (e.g., a 12V signal) tomerchant terminal 110 via USB connector 106, and via power supplycircuitry of merchant terminal 110 and USB connector 108, to customerterminal 112.

The electronic interactions between the merchant and the customer maytake place between the merchant terminal 110 and the customer terminal112. In one embodiment, the merchant terminal 110 supports aninteractive computing device that is capable of processing paymentinformation (e.g., encrypted payment card data and user authenticationdata) and transaction information (e.g., purchase amount andpoint-of-purchase information) with the customer terminal 112 and aremote payment server (not depicted). The merchant terminal 110 mayinclude a plurality of interfaces as described herein in order toreceive and provide power, to communicate with the customer terminal 112and other devices such as a remote payment server, and to physicallyinterface with other components such as the customer terminal 112. Theinteractive computing device of the merchant terminal 110 may executethe software instructions of a point-of-sale application to manage userinteractions with a merchant, communications with the customer terminal112, and communications with remote payment servers. The merchant isprovided an interface through which the merchant can enter selections ofpurchased items, access customer information (e.g., loyaltyinformation), check inventory, calculate taxes and fees, and otherwiseperform necessary customer service and transaction steps.

The customer terminal 112 may operate as a payment terminal thatreceives payment information from a customer, and may provide a varietyof interfaces to interact with the merchant terminal 110 and a customer.A user interface of the customer terminal 112 may allow the user tointeract with the customer terminal 112 in order to interact with themerchant (e.g., select items for purchase, answer queries, confirmpurchases, provide PINs and signatures, etc.), receive paymentinformation (e.g., from a swipe card, chip card, or NFC-enabled paymentdevice) from a customer, communicate with the merchant terminal 110(e.g., via USB connector 108), receive power from merchant terminal 110(e.g., via USB connector 108), and physically attach to the merchantterminal 110 (e.g., via connecting enclosures of each of the customerterminal 112 and the merchant terminal 110).

FIG. 2 depicts a block diagram of an example merchant terminal 110 inaccordance with some embodiments of the present disclosure. Althoughparticular components are depicted in a particular arrangement in FIG.2, it will be understood that merchant terminal 110 may includeadditional components, one or more of the components depicted in FIG. 2may not be included in merchant terminal 110, and the components ofmerchant terminal 110 may be rearranged in any suitable manner. Althoughit will be understood that merchant terminal 110 of point-of-sale system100 may be implemented in any suitable manner, in one embodiment themerchant terminal 110 may comprise a first USB interface 202, a secondUSB interface 203, a power management device 204, a USB control circuit206, a processing unit 208, a user interface 210, an audio device 212, adebug module 214, a wired interface 216, a wireless interface 218, and amemory 220.

Processing unit 208 of merchant terminal 110 may include a processorcapable of performing the processing functions of the merchant terminal110 as described herein, and may be embodied by any suitable hardware,software, memory, and circuitry as is necessary to perform thosefunctions. Processing unit 208 may include any suitable number ofprocessors, and may perform the operations of merchant terminal 110based on instructions in any suitable number of memories and memorytypes. In an example embodiment, the processing unit 208 may be aSystem-on-Chip (SoC) processer having a dual-core processor (e.g., aDual core ARM Cortex A7/A9).

Processing unit 208 may execute instructions stored in memory 220 ofmerchant terminal 110 to control the operations and processing ofmerchant terminal 110, and memory 220 may also store informationnecessary for the operation of merchant terminal 110. As used herein,memory may refer to any suitable tangible or non-transitory storagemedium. Examples of tangible (or non-transitory) storage medium includedisks, thumb drives, and memory, etc., but does not include propagatedsignals. Tangible computer readable storage medium include volatile andnon-volatile, removable and non-removable media, such as computerreadable instructions, data structures, program modules or other data.Examples of such media include RAM, ROM, EPROM, EEPROM, SRAM, flashmemory, disks or optical storage, magnetic storage, or any othernon-transitory medium that stores information that is accessed by aprocessor or computing device. In an example embodiment, memory 220 mayinclude a flash memory and a RAM memory (e.g., a 16 GB eMMC NAND flashand a 2 GB LPDDR3 RAM).

First USB interface 202 and second USB interface 203 may provide forconnection of other devices or components to the merchant terminal 110as appropriate. Although any type of USB connector and interface may beused in accordance with the present disclosure, in an embodiment each offirst USB interface 202 and second USB interface 203 may be a USB type Breceptacle for interfacing with a type B connector of a USB connector(e.g., USB connector 106 or 108, for connecting to USB hub 104 orcustomer terminal 112). As will be described herein, in an embodimentfirst USB interface 202 and second USB interface 203 may beinterchangeable, such that merchant terminal 110 may function in anidentical manner regardless of which of the USB interfaces is coupled toUSB hub 104 or customer terminal 112. In some embodiments (not depictedin FIG. 2), the merchant terminal 110 may include additional interfaces,such additional USB ports, Lightning, Firewire, Ethernet, etc.

Although power may be provided to merchant terminal 110 in any suitablemanner, in an embodiment, DC power may be provided from USB hub 104 whenit is connected to the merchant terminal via first USB interface 202 orsecond USB interface 203. A USB control circuit 206 may includecircuitry for interacting with the USB hub 104 to receive the incomingDC power signal and to distribute that signal to other components of themerchant terminal 110 (e.g., via power management device 204) and to thecustomer terminal 112 (e.g., via the other USB interface of first USBinterface 202 and second USB interface 203). A power management device204 (e.g., a discrete power management integrated circuit) may receivepower provided from USB hub 104 through one of the USB interfaces (firstUSB interface 202 or second USB interface 203) and USB control circuit206, and may perform functions related to power requirements of a hostsystem (e.g., DC to DC conversion, battery charging, linear regulation,power sequencing and other miscellaneous system power functions).

Merchant terminal 110 may also include a user interface 210. Userinterface 210 may provide various interfaces and outputs to the merchantterminal 110 to be viewed by a merchant. An example user interface 210may include hardware and software for interacting with a user, such as atouchscreen interface, voice command interface, keyboard, mouse, gesturerecognition, any other suitable user interface, or any combinationthereof. In one embodiment, the user interface 210 may be a touchscreeninterface that displays an interactive user interface for programs andapplications such as a point-of-sale application running on the merchantterminal 110.

Merchant terminal 110 may also include an audio device 212. Audio device212 may provide audio for the merchant terminal 110. An example audiodevice 210 may comprise an audio amplifier and a speaker for providingappropriate audio for the merchant terminal 110.

Merchant terminal 110 may also include a debug module 214. In anembodiment, a debug module may provide an interface and processing forperforming debug operations (e.g., by a technician utilizing a debugdevice), such as identifying and removing defects that prevent correctoperation of the merchant terminal 110 and the various componentsthereof.

Merchant terminal 110 may also include a wired interface 216, which mayinclude any suitable interface for wired communication, such as USB,Lightning, FireWire, Ethernet, any other suitable wired communicationinterface, or any combination thereof, to perform, for example, thewired communication with other devices of the payment system 100 andpayment servers (e.g., via a secure internet connection).

Merchant terminal 110 may also include a wireless communicationinterface 218. The wireless communication interface 218 may include anysuitable hardware and software for providing a wireless communicationinterface such as Bluetooth classic, Bluetooth low energy, WiFi,cellular, short message service (SMS), NFC, any other suitable wirelesscommunication interface, or any combination thereof. In an exampleembodiment, the wireless communication interface 218 may facilitatecommunications between the merchant terminal 110 and peripherals, aswell as with payment servers (e.g., via a secure internet connection).

FIG. 3 depicts a block diagram of an example customer terminal 112 inaccordance with some embodiments of the present disclosure. Althoughparticular components are depicted in a particular arrangement in FIG.3, it will be understood that customer terminal 112 may includeadditional components, one or more of the components depicted in FIG. 3may not be included in customer terminal 112, and the components ofcustomer terminal 112 may be rearranged in any suitable manner. In oneembodiment, customer terminal 110 may comprise a USB interface 302, apower management device 304, a debug module 306, an audio device 308, auser interface 310, a main processing unit 312, a memory 314, a secureenclave 340, a magnetic swipe slot 330, an EMV slot 332, and an NFC flexcircuit 334.

Main processing unit 312 of customer terminal 112 may include aprocessor capable of performing the processing functions of the customerterminal 112 as described herein, and may be embodied by any suitablehardware, software, memory, and circuitry as is necessary to performthose functions. Main processing unit 312 may include any suitablenumber of processors, and may perform the operations of customerterminal 112 based on instructions in any suitable number of memoriesand memory types. In an example embodiment, the main processing unit 312may be a System-on-Chip (SoC) processer having a dual-core processor(e.g., a Dual core ARM Cortex A7/A9).

Main processing unit 312 may execute instructions stored in memory 314of customer terminal 112 to control the operations and processing ofcustomer terminal 112, and the memory 314 may also store informationnecessary for the operation of customer terminal 112. In an exampleembodiment, memory 314 may include a flash memory and a RAM memory(e.g., a 16 GB eMMC NAND flash and a 2 GB LPDDR3 RAM).

USB interface 302 may provide for a connection to the merchant terminal110 in order to receive power from merchant terminal 110 and tocommunicate with the merchant terminal 110. Although any type of USBconnector and interface may be used in accordance with the presentdisclosure, in an embodiment USB interface 302 may be a USB type Breceptacle for interfacing with a micro USB type B connector of a USBconnector (e.g., USB connector 106 or 108, for connecting to merchantterminal 110). In some embodiments (not depicted in FIG. 3), customerterminal 112 may include additional wired or wireless interfaces such asadditional USB ports, Lightning, Firewire, Ethernet, WiFi, Bluetooth,etc.

Although power may be provided to customer terminal 112 in any suitablemanner, in an embodiment DC power may be provided from merchant terminal110 when it is connected to the customer terminal 112 via the USBinterface 302. A USB control circuit 303 may include circuitry forinteracting with the merchant terminal 110 to receive the incoming DCpower signal and to distribute that signal to other components of thecustomer terminal 112 (e.g., via power management device 304). In someembodiments, USB control circuit 303 may enable additionalfunctionality, such as initiating a reprogramming mode for the customerterminal based on a received voltage at USB interface 302 (e.g., at anID pin of USB interface 302). A power management device 304 (e.g., adiscrete power management integrated circuit) may receive power providedfrom merchant terminal 110 through the USB interface 302 and USB controlcircuit 303, and may perform functions related to power requirements ofthe customer system (e.g., DC to DC conversion, battery charging, linearregulation, power sequencing and other miscellaneous system powerfunctions).

Customer terminal 112 may also include a user interface 310. Userinterface 310 may provide various interfaces and outputs to the customerterminal 112 to be viewed by a customer. An example user interface 310may include hardware and software for interacting with a customer, suchas a touchscreen interface, voice command interface, keyboard, mouse,gesture recognition, any other suitable user interface, or anycombination thereof. In one embodiment, the user interface 310 may be atouchscreen device that displays an interactive user interface for thecustomer to engage in purchase transactions (e.g., select items forpurchase, answer queries, confirm purchases, provide PINs andsignatures, etc.) at the customer terminal 112.

Customer terminal 112 may also include an audio device 308. Audio device308 may provide audio for the customer terminal 112. An example audiodevice 308 may comprise an audio amplifier and a speaker for providingappropriate audio for the customer terminal 112.

Customer terminal 112 may also include a debug module 306. In anembodiment, a debug module 306 may provide an interface and processingfor performing debug operations (e.g., by a technician utilizing a debugdevice), such as identifying and removing defects that prevent correctoperation of the merchant terminal 110 and the various componentsthereof.

The secure enclave 340 may be a secure portion of the customer terminal112 that performs critical functionality such as interacting withpayment devices and cryptography, and that stores sensitive informationsuch as cryptographic keys, passwords, and user information. In anembodiment, the secure enclave 340 may be located in a distinct locationof the customer terminal 112 to isolate the secure enclave 340 fromother circuitry of the customer terminal 112 and to allow protectivemeasures (e.g., tamper detection switches, anti-tamper meshes,anti-tamper domes, isolated compartments, etc.) to be installed near andaround the secure enclave 340 (not depicted in FIG. 3). In an exampleembodiment, the secure enclave 340 may be situated at a base of thecustomer terminal 112 in a manner that provides additional clearance forprotective measures.

In an embodiment, the secure enclave 340 may include a secure processingunit 316, a user interface 318, a battery 320, a debug module 322, amagnetic swipe interface 324, a chip card interface 326, and an NFCinterface 328.

Although secure processing unit 316 may be implemented with any suitableprocessor, hardware, software, or combination thereof, in an embodiment,secure processing unit 316 may be implemented as microcontroller such asthe K21 microcontroller unit (MCU) supplied by Freescale Semiconductor,Inc. Secure processing unit 316 may perform transaction processing andcryptographic operations, based on instructions and information (e.g.,customer data, encryption keys, etc.) stored in a memory of secureprocessing unit 316 (not separately depicted in FIG. 3), which may beany suitable memory as described herein. Secure processing unit 316 maycommunicate with main processing unit 312 in order to receive andrespond to requests for processing of payment information.Communications may be performed using any suitable internal bus andcommunication technique (e.g., UART, SPI, I²C, and GPIO).

The secure enclave 340 of customer terminal 112 may also include abattery 320. In some embodiments, the battery 320 may function as aprimary power source to certain components of the secure enclave 340(e.g., memory storing critical payment, customer, and encryptioninformation), such that when the battery power is removed theinformation is lost. The battery 320 may function in this manner inresponse to a tamper attempt, such that in response to the tamperattempt, the secured information is destroyed.

The secure enclave 340 of customer terminal 112 may also include a debugmodule 322. In an embodiment, a debug module 322 may provide aninterface and processing for performing debug operations (e.g., by atechnician utilizing a debug device) directly with the components of thesecure enclave.

The secure enclave 340 of customer terminal 112 may also include a userinterface 318. In an embodiment, user interface 318 (e.g., a keypad,touchscreen, etc.) may be located within the secure enclave such thatcertain content is provided to the secure enclave 340 rather than thegeneral processing circuitry of the customer terminal 112. In thismanner, critical information such as PIN numbers, signatures, andpasswords may be provided only to the secure enclave 340 in the firstinstance, and then forwarded to the main processing unit 312 inencrypted or unencrypted form, as required.

Secure enclave 340 of customer terminal 112 may also include a magneticswipe interface 324, chip card interface 326, and NFC interface 328.Each of these components may include interface circuitry for receivingand processing signals from a payment interface, such as a magneticreader head 330, a chip card slot 332 (e.g., providing power andcommunications to the chip card), and an NFC circuit, components ofwhich may be located on an NFC flex circuit 334 remote from secureenclave 340.

In an embodiment, if a secure enclave 340 is located at the base of thecustomer terminal 112, it may be desired for the NFC antenna and certainrelated circuitry (e.g., voltage boost circuitry, matching circuitry,EMC circuitry, and receive filters and amplifiers) to be located at adifferent location of the customer terminal 112 remote from the secureenclave 340, such as a NFC tap target area near the top center of thecustomer terminal.

FIG. 4 depicts example steps 400 for performing a payment transactionwith a merchant terminal 110 and a customer terminal 112 in accordancewith some embodiments of the present disclosure. While, for purposes ofsimplicity of explanation, the methods described herein are shown anddescribed as a series of steps, it is to be understood and appreciatedthat such illustrations or corresponding descriptions are not limited bythe order of the steps, as some steps may occur in different ordersand/or concurrently with other steps from what is depicted and describedherein. Any non-sequential, or branched, flow illustrated via aflowchart should be understood to indicate that various other branches,flow paths, and orders of the steps, can be implemented which achievethe same or a similar result. Moreover, not all illustrated steps may berequired to implement the methods described hereinafter.

At step 402, the point-of-sale application can be displayed at userinterface 210 of merchant terminal 110. The point-of-sale applicationmay display information such as items available for sale, specials,coupons, available inventory, combinations, and other similarinformation that may be used to guide a merchant user through atransaction. Processing may then continue to step 404.

At step 404, merchant terminal 110 may receive purchase information fromthe merchant interaction with the point of sale application of the userinterface 210, such as selections of items for purchase, selections ofoptional purchases, and other information regarding a purchase. Once thepurchase information has been received, processing may continue to step406.

In some embodiments, at step 406, merchant terminal 110 may communicatewith customer terminal 112 to perform a portion of the transactionsteps. For example, a customer may interact with user interface 310 ofcustomer terminal 112 to select items to purchase, select options, entercoupons, enter customer or loyalty information, confirm a purchase, orperform other similar tasks. Once the merchant terminal 110 and customerterminal 112 have completed any required communications, processing maycontinue to step 408.

At step 408, the merchant terminal 110 may complete the transactionselections based on the inputs and information received at steps 404 and406 in order to initiate a check-out procedure. At this point in thetransaction, required amounts such as tax and tip may be added to thepurchase amount, such that the transaction may be completed. Processingmay then continue to step 410.

At step 410, the merchant terminal 110 may provide a final paymentamount to the customer terminal 412 and request that the customerprovide a payment method. Information relating to the transaction andinstructions may be provided to the customer at user interface 310 ofthe customer terminal 112. Processing may then continue to step 412.

At step 412, the customer terminal 112 may receive payment informationfrom the customer via one of the magnetic stripe slot 330, chip cardslot 332, or NFC antenna of NFC flex circuit 334. In some embodiments,user inputs such as PIN number, password, or signature may also beprovided at user interface 318. The secure enclave 340 may process andencrypt the received payment information and provide it to merchantterminal 110. Processing may then continue to step 414.

At step 414, the merchant terminal 110 may contact a payment server orsimilar remote entity in order to determine whether the transaction isauthorized. In an embodiment, the merchant terminal 110 may transmit theencrypted payment information as well as other information about thetransaction to the payment via a communication interface such as wiredinterface 216 or wireless interface 218. Processing may then continue tostep 416.

At step 416, merchant terminal 110 may receive a response from thepayment server, such as an approval or denial of the transaction.Processing may then continue to step 418, at which notice of theapproval or denial may be provided to the merchant and customer via userinterface 210 of merchant terminal 110 and the customer via userinterface 310 of customer terminal 112.

FIG. 5 depicts a block diagram of a near field communication (NFC)circuit 500 in accordance with some embodiments of the presentdisclosure. Although particular components are depicted in a particulararrangement in FIG. 5, it will be understood that NFC circuit 500 mayinclude additional components, one or more of the components depicted inFIG. 5 may not be included in NFC circuit 500, and the components of NFCcircuit 500 may be rearranged in any suitable manner. The NFC circuit500 includes circuitry for generating and/or modulating a carrier signalto communicate with an NFC payment device 544. The NFC circuit 500 canhave an NFC interface portion 328 connected to an NFC flex portion 334.As previously discussed in the disclosure, the NFC interface 328 can bepart of the secure payments enclave 340 and can be located in the baseof the customer terminal 112. In one embodiment, the components of theNFC interface 328 can be mounted on a printed circuit board (PCB), butcan be mounted on other structures (e.g., a flex circuit) in otherembodiments. The NFC flex 334 can be coupled to the NFC interface 328and extend from the secure payment enclave 340 in the base of thecustomer terminal 112 to another location in the customer terminal 112,such as an NFC tap target area associated with the user interface 310.In one embodiment, the NFC flex 334 can extend to a top, center locationof the customer terminal 112 such that the circuitry 506 of the NFC flex334, including the NFC antenna 540, is located in a position tofacilitate communication with an NFC payment device 544 carried by thecustomer.

The NFC payment device 544 may be an electronic device such as a smartphone, tablet, or smart watch that is capable of engaging in securetransactions with customer terminal 112 (e.g., via communications withNFC circuit 500). The NFC payment device 544 may have hardware (e.g., asecure element including hardware and executable code) and/or software(e.g., executable code operating on a processor in accordance with ahost card emulation routine) for performing secure transactionfunctions. During a payment transaction, the NFC payment device 544 maybe inductively coupled to NFC circuit 500 via a near field 542 and maycommunicate with customer terminal 112 by active or passive loadmodulation of a wireless carrier signal provided by NFC circuit 500 inaccordance with one or more wireless communication standards such as ISO14443 and ISO 18092. The NFC circuit 500 of customer terminal 112 cancommunicate information to the NFC payment device 544 by changing theamplitude and/or phase of the wireless carrier signal based on data tobe transmitted from the customer terminal 112. In one embodiment, theNFC circuit 500 can emit a wireless carrier signal having a suitablefrequency (e.g., 13.56 MHz) to generate the near field 542 for the NFCpayment device 544. If the NFC payment device 544 has a suitably tunedantenna within the range of the near field 542 (e.g., 0 to 10 cm), theNFC payment device 544 receives the wireless carrier signal or wirelessdata signal that is transmitted by NFC circuit 500. In the case of awireless data signal, processing circuitry of the NFC payment device 544is able to demodulate the received signal and process the data that isreceived from the NFC circuit 500.

In one embodiment, the circuitry 506 of the NFC flex 334 can be locatedat an “electrically long” distance of between about 2 inches and about10 or more inches from the NFC interface 328. The trace(s) (or line(s))connecting the NFC interface 328 and the circuitry 506 of the NFC flex334 can be considered “electrically long” when the distance travelled bythe trace(s) is at least about 2.5% to about 5% or more of thepropagation-medium-specific wavelength of the signal being transmittedon the trace(s) (e.g., a carrier signal from the NFC transceiver 510).In other words, if the length of the trace(s) connecting the NFCinterface 328 and the circuitry 506 of the NFC flex 334 is between about1/40^(th) and about 1/20^(th) or more of the wavelength of the signalbeing transmitted over the trace(s), then the connection between the NFCinterface 328 and the NFC flex 334 can be considered “electricallylong.” Signals transmitted in an “electrically long” transmission lineare susceptible to interference and/or degradation by improper impedancecontrol and may also radiate energy that may impact other signals of thecustomer terminal. For example, transmission line effects may occur inan “electrically long” connection thereby resulting in reflections thatdistort the signal being transmitted in the trace.

The NFC interface 328 can include an NFC transceiver 510. In anembodiment, the NFC transceiver may receive data 502 such as paymentmessages to be transmitted via NFC communications. Based on the receiveddata and modulation procedures, an outgoing data signal (e.g., a carriersignal modulated with payment data) may be communicated to the NFC flex334 for transmission by the NFC antenna 540 to the payment device 544via near field 542. The NFC interface 328 can also include a secondamplifier circuit 570 that receives data from a first amplifier circuit560 on the NFC flex 334. The second amplifier circuit 570 is coupled toa comparator circuit 580 that can digitize and provide an incomingdigital signal to the NFC transceiver 510. In one embodiment, the NFCtransceiver 510 can be coupled to the secure processing unit 316 viacommunication interfaces or buses (e.g., I²C, SPI, UART, and GPIO) toreceive data 502 (e.g., payment messages) to be transmitted and toprovide data 502 (e.g., payment messages) to the secure processing unit316.

The NFC flex 334 can include a power amplifier circuit 520 that receivesa carrier signal or modulated digital signal from the NFC transceiver510. The power amplifier circuit 520 is connected to tuning circuits 530that tune the output of the power amplifier circuit 520 and provide theresulting signal to the NFC antenna 540 for transmission to the NFCpayment device 544. The NFC antenna 540 can receive messages from theNFC payment device 544 and provide the received messages torectifier/filtering circuits 550. The rectifier/filtering circuits 550can remove the carrier signal from the received message and provide thedata from the reply message to the first amplifier circuit 560, whichcommunicates with the second amplifier circuit 570 as discussed above.

FIG. 6 depicts a schematic diagram of the NFC flex 334 in accordancewith some embodiments of the present disclosure. Although particularcomponents are depicted in a particular arrangement in FIG. 6, it willbe understood that NFC flex may include additional components, one ormore of the components depicted in FIG. 6 may not be included in NFCflex 334, and the components of NFC flex 334 may be rearranged in anysuitable manner. In one embodiment, NFC flex 334 is a flexible circuit,flex circuit or flexible printed circuit board that can have one or morelayers (e.g., 3 layers) with traces and/or components on each of thelayers. The NFC flex 334 can also provide for interconnections betweenthe layers. While the NFC flex 334 of FIG. 6 shows all components andtraces on a top surface of the NFC flex 334, it is to be understood thatthe components and/or traces may be located on other layers of the NFCflex 334.

The NFC flex 334 includes an interface 508 for coupling the NFC flex 334and NFC interface 328. The interface 508 can be connected to thecircuitry 506 by a plurality of traces (or lines) 606. It is to beunderstood that while 3 traces 606 are shown in FIG. 6, the number oftraces 606 can be greater or less than the number shown in FIG. 6,depending on the number of terminals associated with interface 508 andthe components of circuit 506 to be connected to interface 508. Theinterface 508 and traces 606 can be used to send and receive signalsbetween the circuitry 506 of the NFC flex 334 and the NFC interface 328.In one embodiment, the interface 508 and traces 606 can be used toexchange a differential transmit signal, a receive signal, one or morepower signals and one or more additional signals between the NFCinterface 328 and the circuitry 506 of the NFC flex 334.

The NFC flex 334 can include a first portion 602 and a second portion604. The interface 508 can be mounted on the first portion 602 near theNFC interface 328. The first portion 602 can be sized to be ableaccommodate the traces and/or lines connecting the interface 508 and thecircuitry 506. In one embodiment, the first portion 602 can have alength that is greater than its width. The second portion 604 of the NFCflex 334 can be located near the top of the merchant terminal 112 andcan be sized to incorporate the circuitry 506, including antenna 540. Inone embodiment, the second portion 604 can have a larger width than thefirst portion 602 since the second portion has to have adequate spacefor antenna 540 and circuitry 506. The second portion 604 of the NFCflex 334 can include one or more additional layers (e.g., stiffenerlayers, ferrite layers and PSA layers) to provide additional rigidity tothe second portion 604 for the mounting of the components of circuit 506(including antenna 540). In one embodiment, the second portion 604 ofthe NFC flex 334 (or a portion thereof) can include a printed circuitboard instead of a flexible circuit element.

In the embodiment shown in FIG. 6, the NFC flex 334 can include anauxiliary antenna 592 that is coupled to auxiliary circuitry 594. Theauxiliary antenna 592 can be selectively switched on and off asnecessary to modify the overall inductive load during NFCcommunications. In one embodiment, the auxiliary antenna 592 may beswitched on during times when the NFC antenna 540 in NFC circuit 500 isnot transmitting a modulated data signal, in order to modify theinductive load and assist in receiving a modified signal from the NFCpayment device 544.

FIG. 7 depicts a schematic diagram of an NFC transceiver 510 inaccordance with some embodiments of the present disclosure. Althoughparticular components are depicted in a particular arrangement in FIG.7, it will be understood that the NFC transceiver 510 may includeadditional components, one or more of the components depicted in FIG. 7may not be included in the NFC transceiver 510, and the components ofNFC transceiver 510 may be rearranged in any suitable manner. The NFCtransceiver 510 can include a processing device 512 and a drive circuit514. The drive circuit 514 can be coupled to the power amplifier circuit520 through interface 508 and the first portion 602 of the NFC flex 334.The processing device 512 can have two output terminals (OUT-A, OUT-B)to provide a differential, amplitude modulated, digital signal to thedrive circuit 514. In one embodiment the differential, amplitudemodulated digital signal can be either a wireless carrier signal or anoutgoing modulated digital signal. A wireless carrier signal may be asignal having a fixed frequency such as 13.56 MHz, while the outgoingmodulated digital signal may modify the wireless carrier in a suitablemanner (e.g., amplitude modulation) in order to encode data onto thewireless carrier signal based on payment messages to be transmitted(e.g., based on data 502). The differential signal from the processingdevice 512 can have a positive signal on one line and a negative signalin the other line.

In one embodiment, the processing device 512 can be a field programmablegate array (FPGA) or other similar type of device, e.g., amicroprocessor. The drive circuit 514 can include a resistor connectedin parallel with an inverter for each of the lines used for thedifferential signal. As shown in FIG. 7, resistor R1 and inverter INV1can be connected to terminal OUT-A and resistor R2 and inverter INV2 canbe connected to terminal OUT-B. The resistors R1 and R2 and theinverters INV1 and INV2 can be selected to provide bufferingcapabilities and the desired drive and impedance characteristics forcommunicating with the power amplifier circuit 520 and to reduce orremove any transmission line effects that may occur during thecommunication of the differential, amplitude modulated, digital signalbetween the drive circuit 514 and the power amplifier circuit 520.

During periods when modulation is applied to the wireless carrier signal(i.e., transmit periods) based on the outputs from the processing device512, a modulated wireless signal is output from the antenna 540. Themodulated wireless signal varies from the wireless carrier signal in itsamplitude, phase, or both in response to received payment messages(e.g., received as data 502). Processing device 512 may implement amodulation procedure in order to generate the modulated wireless signal,either alone or in combination with modulation circuitry. The modulatedwireless signal is provided to the power amplifier circuit 520 andtransmitted over antenna 540 (i.e., via drive circuit 514, interface508, and traces 606) as a modulated wireless signal (representing datato be transmitted) during a transmit event. The processing device 512can also provide a wireless carrier signal to the NFC flex 334 fortransmission via the antenna 540 when data is not being transmitted fromthe processing device 512.

The processing device 512 may determine data from received signals byextracting a data signal from the signal provided to the processingdevice. As described herein, the various components within the receivepath may provide an incoming digital data signal to the processingdevice (e.g., from comparator circuit 580). The processing device 512may utilize information about a known encoding procedure to determinedata from the digital data signal. The determined data may then beprovided to other processing circuitry via communication interface aspayment messages (e.g., as data 502).

FIG. 8 depicts a schematic diagram of a power amplifier circuit 520 inaccordance with some embodiments of the present disclosure. Althoughparticular components are depicted in a particular arrangement in FIG.8, it will be understood that the power amplifier 520 may includeadditional components, one or more of the components depicted in FIG. 8may not be included in the power amplifier 520, and the components ofthe power amplifier 520 may be rearranged in any suitable manner. In anembodiment, the power amplifier circuit 520 can include a terminationcircuit 522 and an amplifier circuit 524.

Although the termination circuit may be configured in a variety ofmanners, in an embodiment, the termination circuit 522 can include apair of resistors connected in parallel for each of the traces 606 usedfor the differential signal from the NFC transceiver 510. The output ofthe termination circuit 522 can be connected to terminals of theamplifier circuit 524. As shown in FIG. 7, resistors R3 and R6 can beconnected to terminal IN-A of amplifier circuit 524 and resistors R4 andR5 can be connected to terminal IN-B of amplifier circuit 524. Theconfiguration and values for components of the termination circuit 522can be arranged to match the impedance of the traces 606 and/orinterface 508 connecting the power amplifier circuit 520 and NFCtransceiver 510, in order to reduce or remove any signal reflectionsthat may occur at the power amplifier circuit 520 when receiving theoutgoing modulated digital signal (e.g, the differential, amplitudemodulated, digital signal) from the drive circuit 514. The resistorsR3-R6 can be selected to match the impedance of the lines connected tothe power amplifier circuit 520 (e.g., the traces 606 in the firstportion 602 of the NFC flex 334).

The amplifier circuit 524 can be used to convert the outgoing modulateddigital signal to a modulated analog signal and to boost the amplitude(voltage) of the analog signal. In one embodiment, the amplifier circuitcan include an H-Bridge circuit. The analog signal output from theamplifier circuit 524 can include the desired data signal and carrierfrequencies, and, in some instances, one or more harmonic frequencies.The amplifier circuit 524 can boost the amplitude of the analog signalbased on a low drop out (LDO) signal received at terminal VH from an LDOcircuit 526. The LDO circuit 526 can receive a buck signal of about 5 Vto about 10 V from the NFC interface 328. The LDO circuit 526 caninclude a voltage regulator to adjust the buck signal from the NFCinterface 528 to a desired voltage for the amplifier circuit 524 (e.g.,50 volts). The amplifier circuit 524 can then use the signal from theLDO circuit 526 in establishing the amplitude of the analog signalprovided by the amplifier circuit 524.

FIG. 9 depicts a schematic diagram of the tuning circuit 530 and antenna540 in accordance with some embodiments of the present disclosure.Although particular components are depicted in a particular arrangementin FIG. 9, it will be understood that the tuning circuit 530 may includeadditional components, one or more of the components depicted in FIG. 9may not be included in the tuning circuit 530, and the components of thetuning circuit 530 may be rearranged in any suitable manner. In oneembodiment, the tuning circuit 530 can remove harmonics from thedifferential analog signal received from the power amplifier circuit520. The differential analog signal (e.g., the wireless carrier signaland/or modulated wireless signal) from tuning circuit 530 is thentransmitted over antenna 540. The tuning circuit 530 can include anelectromagnetic compatibility (EMC) circuit 532 and a matching circuit534.

The differential analog signal from the power amplifier circuit 520 canbe provided to EMC circuit 532. In some embodiments, EMC circuit 532 mayinclude an electromagnetic interference (EMI) filter for suppressinginterference experienced by NFC circuit 500, and may include one or morecomponents such as inductors and/or capacitors in order to provideacceptable electromagnetic compatibility with other high-frequencysignals. The output of EMC circuit 532 may be provided to matchingcircuit 534. Matching circuit 534 may include suitable components suchas resistors, inductors, and capacitors to provide for impedancematching and tuning of antenna 540. In one embodiment, the components ofEMC circuit 532 and matching circuit 534 (e.g., resistors, inductors,and capacitors) modify the output waveform of the wireless carriersignal. In other embodiments, the tuning circuit 530 and/or poweramplifier 520 can operate as a transmit load for the antenna 540. Whentransmitting the wireless carrier signal or modulated wireless signal,the signal characteristics and inductive coupling of antenna 540 arebased on this transmit load.

FIG. 10 depicts a schematic diagram illustrating the rectifier/filteringcircuits and first amplifier circuit in accordance with some embodimentsof the present disclosure. Although particular components are depictedin a particular arrangement in FIG. 10, it will be understood that therectifier/filtering circuit 550 and first amplifier 560 may includeadditional components, one or more of the components depicted in FIG. 10may not be included in the rectifier/filtering circuit 550 and firstamplifier 560, and the components of the rectifier/filtering circuit 550and first amplifier 560 may be rearranged in any suitable manner. Therectifier/filtering circuit 550 can receive and process a receivedsignal from the antenna 540 (e.g., a modulated signal provided bypayment device 544), and may include a rectifier 552 and a filter 554.The first amplifier 560 can include an operational amplifier 562 with afeedback circuit 564.

The rectifier 552 can receive a differential, modulated analog signalfrom antenna 540 and the matching circuit 534 during a receive event.The rectifier 552 can remove the carrier signal from the differential,modulated analog signal received by antenna 540 and provide ademodulated analog data signal to the filter 554. In one embodiment, therectifier 552 can include 4 diodes arranged in a bridge configuration(bridge rectifier). The filter 554 can include an envelope detector thatis centered on the frequency of the data signal from the rectifier 552and can provide a “card proximity” signal to the NFC interface 328 thatcorresponds to an estimated distance between the NFC antenna 540 and thepayment device 544. The card proximity signal can be used to adjust thetransmit power when attempting to communicate with the payment device544. In one embodiment, the filter 554 can include suitable componentssuch as resistors, inductors, diodes and capacitors to generate the cardproximity signal and perform the envelope detection operation.

The operational amplifier 562 and feedback circuit 564 can provide ananalog data signal having a lower frequency and lower amplitude to thesecond amplifier circuit 570. The analog data signal provided by theoperational amplifier 562 and feedback circuit 564 can have a lowerfrequency since the frequency of the data signal can be less than thefrequency of the carrier signal that has been removed by the rectifier552. The operational amplifier 562 and feedback circuit 564 can drop thegain of the analog data signal from the filter 554 and act as a bufferfor the data signal. In addition, the operational amplifier 562 andfeedback circuit 564 can provide low source impedance when communicatingthe analog data signal to the second amplifier 570, which can have hightermination impedance. In one embodiment, the feedback circuit 564 caninclude suitable components such as resistors and capacitors to generatethe desired output from the operational amplifier 562.

FIG. 11 depicts a schematic diagram of the second amplifier circuit andcomparator circuit in accordance with some embodiments of the presentdisclosure. Although particular components are depicted in a particulararrangement in FIG. 11, it will be understood that the second amplifiercircuit 570 and the comparator 580 may include additional components,one or more of the components depicted in FIG. 11 may not be included inthe second amplifier circuit 570 and the comparator 580, and thecomponents of the second amplifier circuit 570 and the comparator 580may be rearranged in any suitable manner. The second amplifier circuit570 can include an input circuit 572, an operational amplifier 574 and afeedback circuit 576. The comparator 580 can include a comparator highcircuit 582 and a comparator low circuit 584.

The second amplifier circuit 570 can receive the analog data signal fromthe first amplifier circuit 560 and can provide the desired gain to theanalog data signal from the first amplifier circuit for subsequentprocessing by the comparator 580 and NFC transceiver 510. The secondamplifier circuit 570 can include an input circuit 572 that can operateas a high pass filter on the analog data signal. The feedback circuit576 can be coupled to the input circuit 572 by resistor R7 and the inputcircuit 572 can also receive feedback from the output of the operationalamplifier 574 via capacitor C1. The input circuit 572 and the feedbackcircuit 576 may include suitable components such as resistors,inductors, and capacitors to provide for the desired filtering effectsand output from the operational amplifier 574.

The comparator circuit 580 can receive the amplified analog data signalfrom the operational amplifier 574 and generate an incoming digital datasignal for NFC transceiver 510. Each of the comparator high circuit 582and the comparator low circuit 584 can receive the output from theoperational amplifier 574 and provide a corresponding input to theprocessing device 512, based on the relative comparator values (high andlow) of the two comparators and the input signal. The comparator highcircuit 582 and the comparator low circuit 584 may each include suitablecomponents such as resistors, inductors, and capacitors to generate thedesired digital data signals for the processing device 512.

The foregoing is merely illustrative of the principles of thisdisclosure and various modifications may be made by those skilled in theart without departing from the scope of this disclosure. The abovedescribed embodiments are presented for purposes of illustration and notof limitation. The present disclosure also can take many forms otherthan those explicitly described herein. Accordingly, it is emphasizedthat this disclosure is not limited to the explicitly disclosed methods,systems, and apparatuses, but is intended to include variations to andmodifications thereof, which are within the spirit of the followingclaims.

As a further example, variations of apparatus or process parameters(e.g., dimensions, configurations, components, process step order, etc.)may be made to further optimize the provided structures, devices andmethods, as shown and described herein. In any event, the structures anddevices, as well as the associated methods, described herein have manyapplications. Therefore, the disclosed subject matter should not belimited to any single embodiment described herein, but rather should beconstrued in breadth and scope in accordance with the appended claims.

What is claimed is:
 1. A customer terminal for processing paymentinformation received via near-field communications (NFC) from a NFCpayment device, the customer terminal comprising: a customer terminalcircuit board comprising: a processing element configured to sendoutgoing payment messages and receive incoming payment messages, whereinthe processing element is further configured to process the paymentinformation based on the outgoing and incoming payment messages; a NFCtransceiver in communication with the processing element to receive theoutgoing payment messages from the processing element, modulate the databased on a carrier signal to generate an outgoing modulated digitalsignal, receive an incoming digital signal, and process the incomingdigital signal to generate the incoming payment messages; an NFC receivecircuit, wherein the NFC circuit comprises: an amplifier circuitconfigured to amplify an analog data signal; and a comparator configuredto receive the amplified analog data signal from the amplifier circuit,and to digitize the amplified analog data signal to generate theincoming digital signal; and a NFC flex circuit, wherein at least aportion of the NFC flex circuit comprises flexible circuit elements, theNFC flex circuit comprising: a NFC transmission circuit, comprising: apower amplifier configured to receive the outgoing modulated digitalsignal from the NFC transceiver and to amplify the outgoing modulateddigital signal to output an outgoing modulated analog signal; a tuningcircuit coupled to the power amplifier to tune the outgoing modulatedanalog signal to generate a tuned outgoing signal; and an antennaconfigured to transmit the tuned outgoing signal and to receive aninductively coupled signal; a flex amplifier circuit configured toreceive the inductively coupled signal from the antenna and amplify theinductively coupled signal to output the analog data signal; one or moretransmit traces coupled to the customer terminal circuit board and theNFC transmission circuit, wherein the outgoing modulated digital signalsare transmitted from the NFC transceiver to the power amplifier via theone or more transmit traces; and a receive trace coupled to the customerterminal circuit board and the flex amplifier circuit, wherein theanalog data signal is provided from the flex amplifier circuit to theNFC receive circuit via the receive trace, wherein the one or moretransmit traces and the receive trace are flexible circuit elements, andwherein the one or more transmit traces and the receive trace extend apredetermined distance between the customer terminal circuit board andthe NFC transmission circuit and the flex amplifier circuit, wherein thepredetermined distance is at least 2.5% of thepropagation-medium-specific wavelength of the carrier signal.
 2. Thecustomer terminal of claim 1, wherein the NFC flex circuit furthercomprises a termination circuit to match an impedance of the one or moretransmit traces, the termination circuit coupled to the one or moretransmit traces and the power amplifier.
 3. The customer terminal ofclaim 1, wherein the customer terminal circuit board further comprisesat least one inverter to drive the outgoing modulated digital signalfrom the NFC transceiver, the at least one inverter being coupled to theone or more transmit traces and the NFC transceiver.
 4. The customerterminal of claim 1, wherein the NFC flex circuit further comprises arectifier/filtering circuit to remove the carrier signal from theinductively coupled signal from the antenna, the rectifier/filteringcircuit being coupled to the antenna and the flex amplifier circuit. 5.A terminal to engage in near-field communications (NFC) with a device,the terminal comprising: a base and a target area for NFCcommunications; a NFC circuit to send and receive NFC messages, the NFCcircuit comprising: a first portion located in the base and a secondportion located adjacent to the target area, the first portion beingcoupled to the second portion by a flexible circuit element; the firstportion of the NFC circuit comprising: a NFC transceiver to generate anoutgoing modulated digital signal and receive an incoming digitalsignal; and a NFC receive circuit configured to amplify an analog datasignal and to digitize the analog data signal to generate the incomingdigital signal for the NFC transceiver; the second portion of the NFCcircuit comprising: a NFC transmission circuit to receive the outgoingmodulated digital signal and to generate a tuned outgoing signal; anantenna configured to transmit the tuned outgoing signal and to receivean inductively coupled signal; and a receive amplifier configured toreceive the inductively coupled signal from the antenna and amplify theinductively coupled signal to output the analog data signal.
 6. Theterminal of claim 5, wherein the second portion of the NFC circuit ismounted on a flexible circuit element.
 7. The terminal of claim 5,wherein the flexible circuit element includes one or more traces tocommunicate signals between the first portion of the NFC circuit and thesecond portion of the NFC circuit, the one or more traces extending apredetermined distance greater than 2 inches.
 8. The terminal of claim7, wherein the predetermined distance is at least 2.5% of thepropagation-medium-specific wavelength of a carrier signal used in theoutgoing modulated digital signal.
 9. The terminal of claim 5, whereinthe NFC transmission circuit comprises: a power amplifier configured toreceive the outgoing modulated digital signal and to amplify theoutgoing modulated digital signal to output an outgoing modulated analogsignal; and a tuning circuit coupled to the power amplifier to tune theoutgoing modulated analog signal to generate the tuned outgoing signal.10. The terminal of claim 9, wherein the NFC transmission circuitcomprises a termination circuit coupled to the power amplifier to matchan impedance of the flexible circuit element coupling the first portionof the NFC circuit and the second portion of the NFC circuit.
 11. Theterminal of claim 9, wherein the NFC transmission circuit comprises alow drop out circuit coupled to the power amplifier to adjust an inputvoltage provided to the power amplifier, wherein an amplitude of theoutgoing modulated analog signal is based on the input voltage.
 12. Theterminal of claim 9, wherein the tuning circuit comprises anelectromagnetic compatibility circuit to provide electromagneticcompatibility with other high-frequency signals and a matching circuitto provide for impedance matching and tuning of the antenna.
 13. Theterminal of claim 5, wherein the target area is adjacent to atouchscreen device of the terminal.
 14. The terminal of claim 5, whereinthe NFC receive circuit comprises: a second receive amplifier configuredto amplify the analog data signal; and a comparator configured toreceive the amplified analog data signal, and to digitize the amplifiedanalog data signal to generate the incoming digital signal.
 15. Theterminal of claim 5, wherein the first portion of the NFC circuitcomprises at least one inverter coupled to the NFC transceiver to drivethe outgoing modulated digital signal from the NFC transceiver.
 16. Theterminal of claim 5, wherein the second portion of the NFC circuitcomprises a second NFC receive circuit coupled to the receive amplifierto remove a carrier signal from the inductively coupled signal from theantenna.
 17. The terminal of claim 16, wherein the second NFC receivecircuit comprises a rectifier circuit and a filtering circuit.
 18. Theterminal of claim 5, wherein the outgoing modulated digital signal is adifferential signal having a positive signal and a negative signal. 19.The terminal of claim 5, wherein the first portion of the NFC circuit ismounted on a printed circuit board.
 20. A method of exchanging messagesbetween a terminal and a device via near-field communications (NFC), themethod comprising: generating an outgoing message for the device with aprocessing element of the terminal; modulating, with a NFC transceiverof the terminal, the outgoing message based on a carrier signal togenerate an outgoing modulated digital signal; communicating theoutgoing modulated digital signal over at least one transmit trace of aflex circuit of the terminal to an NFC transmission circuit of theterminal; generating, with the NFC transmission circuit, an outgoingmodulated analog signal based on the received outgoing modulated digitalsignal; transmitting, with an antenna of the terminal, the outgoingmodulated analog signal to the device; receiving, at the antenna, aninductively coupled signal from the device; generating, with a first NFCreceive circuit of the terminal, an analog data signal based on theinductively coupled signal; communicating, over at least one receivetrace of the flex circuit, the analog data signal to a second NFCreceive circuit; generating, with the second NFC receive circuit, anincoming digital signal based on the analog data signal; processing theincoming digital signal to generate an incoming message with the NFCtransceiver; and receiving the incoming message at the processingelement.
 21. The method of claim 20, further comprising: coupling theNFC transceiver and the NFC transmission circuit with the at least onetransmit trace; and coupling the first NFC receive circuit and thesecond NFC receive circuit with the at least one receive trace.
 22. Themethod of claim 20, wherein generating an outgoing modulated analogsignal comprises: amplifying the outgoing modulated digital signal witha power amplifier to output an outgoing modulated analog signal; tuningthe outgoing modulated analog signal with a tuning circuit to generate atuned outgoing signal; and providing the tuned outgoing signal to theantenna.
 23. The method of claim 20, further comprising matching animpedance of the at least one transmit trace with a termination circuitcoupled to the NFC transmission circuit.
 24. The method of claim 20,wherein generating an incoming digital signal comprises: amplifying theanalog data signal with a receive amplifier to generate an amplifiedanalog data signal; and digitizing the amplified analog data signal witha comparator to generate the incoming digital signal.
 25. The method ofclaim 20, further comprising driving the outgoing modulated digitalsignal from the NFC transceiver with at least one inverter.
 26. Themethod of claim 20, wherein generating an analog data signal comprisesremoving, with a rectifier circuit, a carrier signal from theinductively coupled signal from the antenna to generate a demodulatedsignal.
 27. The method of claim 26, wherein generating an analog datasignal further comprises amplifying, with an amplifier, the demodulatedsignal to output the analog data signal.
 28. The method of claim 20,wherein the at least one receive trace has a predetermined distance ofat least 2.5% of the propagation-medium-specific wavelength of thecarrier signal, and wherein the at least one transmit trace has apredetermined distance of at least 2.5% of thepropagation-medium-specific wavelength of the carrier signal.